Device and Method for Transporting Material Webs and for Fixing Said Webs on a Counter Bearing

ABSTRACT

The aim of the invention is to improve devices ( 3 ) for transporting material webs ( 1 ) and for fixing said webs ( 1 ) on a counter bearing ( 4 ). Said devices ( 3 ) have the following characteristics:
         at least one transport roller ( 2, 2   a,    2   b ) for transporting the material webs ( 1 ) and   means for applying an electrostatic charge (q) to at least parts ( 8 ) of the material web ( 1 ), wherein the electrostatic forces of said charge (q) aid in the fixing of said parts on a counter bearing.
 
The novelty and inventive step of the invention is that at least one transport roller ( 2, 2   a   , 2   b ) comprises means for applying an electrostatic charge (q) to at least parts ( 8 ) of the material web ( 1 ). The invention also claims a method for operating a device of this type.

The invention relates to a device and method for transporting material webs and for fixing said webs on a counter bearing.

Devices having these functions are known in printed literature. Thus U.S. Pat. No. 4,852,820 A and DE 10202462 A1 disclose web-winding devices. In these web-winding devices, material webs or tubes are transported usually by a plurality of transport rollers to a winding core on which the material web is wound up. When the winding core has to be changed, the material web is cut through, fixed on a new winding core and wound up there. Both the aforementioned publications describe modern winding devices—in short winders—which work in a highly automated manner and in which the described process of fixing the start of the web on the new winding core takes place at least to a large extent without an adhesive. In doing so, the described devices utilize the electrostatic attractive force which occurs between the start of the material web and the winding core when the start of the material web is charged electrostatically. The charging of the start of the web is carried out by an electrode located in the vicinity of the last transport roller of the winder over which transport roller the material web moves before it reaches the winding core.

The still unpublished German patent application having the file number 103 21 599 discloses another winding device in which several material webs or material tubes lying upon each other are provided with an electrostatic charge even before they reach the last transport roller of the winder. The goal of this measure is to bring about an adhesive behavior between these material webs or between the upper side and the lower side of the film tube, which adhesive behavior prevents the material webs from being lifted off from one another by their air resistance during their transportation. This method can be used advantageously in all types of devices in which material webs or film tubes are transported. Thus, film tubes are transported over longer distances, for example, in tubular film extrusion units, wherein it is undesirable for the upper side of the tube to get lifted off from the lower side of said tube.

If the words “material webs” are also regarded as a generic term for film tubes and if the term “counter bearing” is used to sum up all types of supports for material webs, such as for example, other film tubes, other material webs and winding cores, then the machines described in the three publications can be characterized as follows:

Said machines are devices for transporting material webs and for fixing said webs on a counter bearing, wherein the device has the following characteristics:

-   -   at least one transport roller for transporting the material webs         and means for applying an electrostatic charge to at least parts         of the material web, wherein the electrostatic forces of said         charge aid in fixing said parts on a counter bearing.

All these devices leave a lot to be desired when it comes to the reliability of the adhesive behavior of the material web on its counter bearing.

It is therefore the object of the present invention to suggest a device using which it is possible to bring about the adhesion of the material web on its counter bearing still more reliably than hitherto possible.

This object is attained by the fact that at least one transport roller comprises means for applying an electrostatic charge to at least parts of the material web.

The scope of improvement of the adhesion behavior by using the measure according to the present invention is astonishing. Evidently, the smaller distance of the material webs from the transport rollers and the fact that the material webs have a direct contact with the transport rollers and that the material webs can also maintain this contact for a certain period of time depending on the wrap angle and the web speed, are mainly responsible for this scope of improvement. Preferred points of use of the present invention are winding devices for film material, wherein paper-rewinding stands also come into question. As mentioned earlier, the present invention can also be used in other machines in which material webs are transported.

Additional exemplary embodiments of the present invention shall become apparent on the basis of this description and the claims.

The individual figures show:

FIG. 1 a A schematic diagram of the winding device of a surface winder

FIG. 1 b A schematic diagram of the winding device of the same surface winder as shown in FIG. 1 b [sic; 1 a]

FIG. 2 a A schematic diagram of the winding device of a turret winder

FIG. 2 b A schematic diagram of the winding device of the same turret winder as shown in FIG. 1 b [sic; 2 a]

FIG. 3 a A sectional view of a transport roller with an example of means for applying a charge to a material web

FIG. 3 b An enlarged section of FIG. 3 a

FIG. 4 a A sectional view of a transport roller with another example of means for applying a charge to a material web

FIG. 4 b An enlarged section of FIG. 4 a

FIG. 1 shows a schematic diagram of the winding device of a surface winder having a contact roller 2 a, which, in the case of the surface winder, is also the last transport roller of the winder that the material web 1 touches before reaching the winding core 4, which plays the role of the counter bearing here, on which the material web is fixed. The other transport roller 2, which fixes the material web on the contact roller 2 a and which is widely used in the case of surface winders, must also be mentioned here.

The electrodes 5, which introduce the charge to the material web, are indicated in the contact roller. On the contact roller 2 a, the transport direction z of the material web 1 is identical to the direction of rotation z of the roller 2 a. When the old material web roll 7 is wound completely, the blade 6 cuts through the material web 1 and the electrodes 5 transfer a charge to the material web, the ends of which are fixed on the new winding core 4 under the influence of the electrostatic forces coming from the charge q.

Due to the especially critical space conditions around the new winding core, surface winders are a preferred point of use for transport rollers 2 a, which include means for applying a charge to parts of the material web.

However, the winding behavior of turret winders—as shown by way of example in DE 102 02 462, DE 102 02 687, DE 102 03 149 and DE 102 02 463—can be improved by the use of such a roller. In such a turret winder, of which the parts that are important for the winding process are sketched in FIG. 2, the material web usually moves over the transport rollers 2 and 2 a onto the old roll 7. When this roll is supposed to be changed, the new winding core 4 is initially backed against the material web 1. Then the material web 1 is cut through and the free end (not illustrated) of the material web 1 is wound on the winding core 4, wherein different methods are known for fixing the free end at first on the winding core 4.

Here also it is advantageous if particularly the last transport roller 2 a, which the material web 1 touches in the transport direction z, before reaching the new winding core 4, is equipped with means for applying a charge q to the material web.

FIGS. 3 and 3 a [sic; 3 a and 3 b] show a sectional view of a transport roller 2 b with an example of means for applying a charge q to a material web. These means cover only a certain angle area of the circumferential surface of the roller 2 b, as shown in FIG. 3 [sic; 3 a]. FIG. 3 a [sic; 3 b], which shows the structure of the means in detail, is an enlarged section of FIG. 3 [sic; 3 a].

The base body 10 of the roller 2 b is often made of metal. It is surrounded by a soft rubber or plastic layer 11, which is often formed in a foam-like manner and preferably consists of polyurethane. In the region, which serves for applying a charge to the film, this layer is either formed to be thinner than in the remaining circumference of the roller or said layer is omitted altogether in this region. In this region, another insulating layer 12 follows which can be made of Teflon, for example. The purpose of this layer is to insulate the current-carrying metal film 13 reliably against the base body 10. The current-carrying metal film 13 is followed by the weakly conducting layer 14 which has greater electrical resistance than metals, but lesser than insulators, like for example the Teflon layer. So-called electrically conductive plastics, which usually consist of macromolecules having a plurality of delocalizable electrons, are used for preparing such a layer. These electrons often emanate from multiple bonds between the atoms of the molecules. In addition, such plastics are made more conductive by the addition (doping) of conductive substances such as metals or graphite.

Even after all these measures, the electrical conductivity of these plastics is less, by several orders of magnitude, than that of metals such as copper, but much higher than that of the common plastics.

The needle-shaped electrodes 15 are located on this weakly conducting layer 14. These electrodes 15 are also held by the layer 14, there being no direct electrical contact between the metal film 13 and the electrodes 15. The needle-shaped electrodes 15 are bordered in their peripheral direction by the circular cylindrical tubes 17, which are open on their front sides. The tubes 17, for their part, are cast in the plastic layer. However, they can also be removed again so that tubular channels remain in the plastic layer 16. The plastic layer 16 is flush with the layer 11 and forms with the latter the circumferential surface of the roller 2 b, which is interrupted only by the openings 18, kept free by the tubes 17. Due to the openings 18, the electrodes 15 have free contact with the surrounding area of the roller although their tips do not protrude beyond the periphery of the roller.

In the axial direction of the roller 2 b—said axial direction not being shown in this sectional view—several electrodes follow one another so that the electrodes can apply a charge to the entire width of a film web moving over the roller. For this purpose, current is applied to the metal film 13, which serves as a common conductor for the electrodes here. This current flows through the weakly conducting layer 14 to the electrodes 15, wherein the layer 14 performs the function of a resistor between the electrodes and the conductor. Charge q is applied from the tips of the electrodes 15 to a material film even across certain air gaps.

The process of charging plastic webs has proven to be particularly effective. However, the method suggested according to the present invention, of fixing other webs, such as for example, paper webs on different counter bearings also entails advantages.

Particularly in the use of transport rollers according to the present invention for fixing the start of a web on a winding core, it has proven to be advantageous if the web end located on the transport roller is held initially on the transport roller by means of a vacuum, in order to then be lifted off by means of an air blast acting on the film like the vacuum from the interior of the roller through air holes in the peripheral surface of said roller. The details of this method can be obtained from DE 101 40 365 A1.

List Of Reference Symbols  1 Material web  2 Transport roller  2a Contact roller  2b Roller  3 Device (according to the main claim)  4 Counter bearing, winding core  5 Electrode  6 Blade  7 Old roll  8 Free end of the material web  9 Air gap 10 Roller base body 11 Plastic layer 12 13 Other insulating layer, Metal film 14 Weakly conducting film 15 Needle-shaped electrodes 16 Plastic layer 17 Tube 18 Openings 19 20 21 22 

1. Device for transporting material webs (1) and for fixing said webs (1) on a counter bearing (4), which device (3) has the following characteristics: at least one transport roller (2, 2 a, 2 b) for transporting the material webs (1) and means for applying an electrostatic charge (25) to at least parts (8) of the material web (1), wherein the electrostatic forces of said charge (25) aid in the fixing of said parts on a counter bearing, characterized in that at least one transport roller (2, 2 a, 2 b) comprises means for applying an electrostatic charge (25) to at least parts (8) of the material web (1).
 2. Device according to claim 1, characterized in that the device comprises a winding device (3), using which the material web (1) can be fixed and wound up on a winding core (4), and that the at least one transport roller (2, 2 a, 2 b), which has means for applying an electrostatic charge (25) to at least parts of the material web (1), is the last roller (2, 2 a, 2 b) before the winding core (4) in the transport direction (z) of the material web (1).
 3. Device according to one of the preceding claims, characterized in that the means for applying an electrostatic charge (25) to at least parts (8) of the material web (1) are contained inside or on the peripheral surface of the transport roller (2, 2 a, 2 b).
 4. Device according to one of the preceding claims, characterized in that the means for applying an electrostatic charge (25) to at least parts (8) of the material web (1) comprise electrically conductive plastic material (27).
 5. Device according to one of the preceding claims, characterized in that the at least one transport roller (2, 2 a, 2 b), which comprises means for applying an electrostatic charge (25) to at least parts of the material web (1), has a plurality of electrodes (15, 27, 31) in the region of its peripheral surface.
 6. Device according to the preceding claim, characterized in that at least one part of the electrodes (15, 27, 31) is shaped in a needle-like manner, wherein the tip of the needle points in the radial direction (r) away from the rotation axis of the transport roller (2, 2 a, 2 b).
 7. Device according to one of the two preceding claims, characterized in that at least one part of the electrodes (15, 27, 31) is located in the radial direction (r) of the transport roller (2, 2 a, 2 b) inside the outer peripheral surface of said roller (2, 2 a, 2 b).
 8. Device according to one of the three preceding claims, characterized in that a voltage is applied to at least one part of the electrodes (15, 27, 31) by a common line (31).
 9. Device according to the preceding claim, characterized in that the common line (31) is formed from a metal film or a metal wire, preferably of copper.
 10. Device according to one of the preceding claims, characterized in that at least one part of the electrodes (15, 27, 31) is connected to their voltage source (34) by means of a resistor (27).
 11. Device according to the preceding claim, characterized in that at least one part of the resistors (27) consists of a conductive plastic material (14).
 12. Device according to the preceding claim characterized in that the electrodes (15, 27, 31) are embedded at least partially in the conductive plastic material (14).
 13. Method for transporting material webs (1) and for fixing said webs (1) on a counter bearing (4), wherein the material webs (1) are conveyed by at least one transport roller (2, 2 a, 2 b), and wherein an electrostatic charge (25) is applied to at least one part of the material web, wherein the electrostatic forces coming from this charge (25) aid in fixing said parts on the counter bearing (4), and is characterized in that the application of the electrostatic charge (25) to at least parts of the material web (1) is carried out with the help of devices (14, 15, 27, 31) integrated in at least one transport roller (2, 2 a, 2 b).
 14. Method according to the preceding claims characterized in that several material webs (1) or material tubes are transported one upon the other and that the charge transferred by the transport roller (2, 2 a, 2 b) to the material web (1) aids in fixing different material webs on top of each other or in fixing the upper side of tubes on the lower side thereof.
 15. Method according to the preceding claim, characterized in that electrostatic charge (25) is transferred from parts of at least two transport rollers (2, 2 a, 2 b) to the material webs (1) or material tubes, and that electrostatic charge (25) is transferred from parts of at least one first transport roller (2, 2 a, 2 b) to the upper material web or the upper side of the material tube and that electrostatic charge (25) is transferred from parts of at least one second transport roller (2, 2 a, 2 b) to the lower material web or the lower side of the film tube.
 16. Method according to one of the preceding claims, characterized in that the charge transferred from parts of at least one transport roller (2, 2 a, 2 b) aid in fixing one end (8) of the material web (1) on a winding core (4), and that when fixing the material web (1) on the winding core (4), the position of the winding core (4) and of the transport roller (2, 2 a, 2 b) is adjusted in such a way relative to one another that an air gap (9) exists between the winding core (2) [sic; 4] and this transport roller (2, 2 a, 2 b).
 17. Method according to the preceding claim, characterized in that the width of the air gap (9) is adjusted to at least 1 millimeter.
 18. Method according to the preceding claim, characterized in that the width of the air gap (9) is adjusted to at least 2 millimeters. 